Oil coating lower portion of final drive housing

Joined
Jul 16, 2013
Messages
15
Location
Gaylord, MI
Bike
2001 Honda ST1100
Last season I started noticing my final drive was moist with a coating of oil on the bottom half of it. I cleaned it off, but I continue to get a thin coating of oil on the housing. I've NEVER noticed a drop of oil on the ground. I did drain and refill the final drive (on center stand, filling only until the level came up to the bottom of the filler hole, so this is not an overfill issue) last season (the coating issue pre-dated the fluid change event).

It's not apparent (to me) what the source of the oil is. I'm guessing the leak is so small that the oil dispersion pattern is created from airflow (it seems to go UP, against gravity, toward the back of the housing). Has anyone encountered leaking filler plugs? Is that a possibility? Since this isn't a pressurized system, I wouldn't think it would take much to prevent oil from leaking from the filler or the drain plugs.

Here's a quick pic I snapped yesterday.
ST final drive oil covering.jpg
I'm in northern MI, and the bike's been sitting since mid-November waiting for the snow to disappear. No drops on the ground at all after sitting in that same spot for several months. Also, it runs/rides great, so no apparent performance issues or noises. Just over 90k miles on the odometer, too.

It's almost time to start riding again, so I figured I might get this issue eliminated before it becomes a problem. Any thoughts?

Thanks! --Chad
 
Joined
Jun 21, 2011
Messages
1,117
Age
70
Location
Ada ( Grand Rapids ) Michigan
Bike
'07 ST 1300 & '91 GW
STOC #
8421
I have had 6 of the last Hondas that would puke F.D. oil , out of the vent cap on top , at temperatures under 45 ? , at the beginning of a ride . What was the temp when this happens to you ?
( I had to replace the vent cap on all the last 3 bikes with a 90? elbow , hose and fuel filter that acted like a expansion tank for the oil which fixed the problem for me on my 3 bikes . You don't have the mess and you don't lose oil level or suck in dirt through the filterless OEM vent cap )
 
Last edited:
OP
OP
Joined
Jul 16, 2013
Messages
15
Location
Gaylord, MI
Bike
2001 Honda ST1100
That's interesting. I didn't document actually WHEN the phenomena began, but I both start and end my riding seasons where temps are well below the 45F you mentioned. Do you find that mid-summer your final drives weren't making a mess with the warmer temps? One thing, though, that makes me think this ISN'T a vent-related issue is that there's NO oil mess at the top of the final drive (at all). I'd think if the FD was puking oil, I'd see evidence of oil higher up on the FD housing than I am...
 
Joined
Sep 4, 2013
Messages
8,114
Location
Cleveland
Bike
2010 ST1300
In your first pic it looks to me like there is a crack in the housing. Am I seeing things? You do know there is an oil seal on the inside of the final drive - but a leak there would not seep outward to neatly coat the bottom half of the casting.

Maybe wash it off, dust the FD w/ talcum powder and check it at the end of each ride?
 
Joined
Mar 21, 2016
Messages
1,133
Location
P.E.I., Canada
Bike
2005 st1300
Be sure the vent isnt clogged. Double check, but i thought someone had an issue with one a couple of weeks back and were wondering how it came out, and the consensus was that it just pulled out. if it does come out easily, pop it out and blow through it to make sure it is not clogged.
 
Joined
Feb 17, 2007
Messages
1,133
Location
Sauk Rapids, MN
Bike
05 ST1300
STOC #
6765
Mine has done the same thing for a few years. Never really been a problem. I have never looked into why. I will follow this.
 
Joined
Jun 3, 2006
Messages
3,512
Location
British Columbia
Bike
2021 RE Meteor 350
The filler plug area appears to be the wettest, so my guess would be you need a new o-ring on that filler cap . . . or, it is loose.
 
Joined
Feb 25, 2016
Messages
4,759
Location
Northumberland UK
Bike
VStrom 650
What oil are you using? Hypoid 80 is the recommended I think.
It looks as though the leak is past the centre seal, behind the wheel spindle nut. This is either because the seal is shot or the breather is blocked causing pressure to build within casing. The breather will pull off upwards with some effort but I think it will be just about buggered by the time it's on the bench.
I would order a new breather, OEM are not expensive, replace this before starting on seals. To start changing diff seals is not easy.
If you were to look around your car/truck diff joints you would find most have oil misting around the flanges.
Hope it helps,
Upt'North.
 
Joined
Apr 9, 2011
Messages
1,024
Location
Canton, GA
Bike
2006 ST1300
Is the level ever low? Mine does this once in a while, as did both my BMW's before it. The level never drops though, significantly, so I gave up on worrying about it. * In my OLDER BMW, ( 1971 R75/5), using synthetic gear oil caused a pretty bad seepage. Using dino based oils cured it in a few thousand miles. I do use synthetic gear oil in the ST, but the seepage is never THAT bad....at least not enough to worry me.
 
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
The filler plug area appears to be the wettest, so my guess would be you need a new o-ring on that filler cap . . . or, it is loose.
I hate to agree with Mr. Bush, but :plus1:

Remove the fill plug and try wrapping a few turns of teflon tape to threads of the plug before re-installing it. Check to make sure the cap isn't cracked. I understand that's easy to do, if it is tightened too much.

80W was recommended way back when the bike was manufactured, but that is ancient, now. I use 80W-90 ( regular or synthetic ) or 80-140 synthetic , BTW w/o any seepage.
 
Last edited:
OP
OP
Joined
Jul 16, 2013
Messages
15
Location
Gaylord, MI
Bike
2001 Honda ST1100
Great suggestions. I don't really recall feeling a notable "bite" by the o-ring on the filler cap when I tightened it down, but didn't re-remove the filler cap to check the status of the o-ring. I'm making a parts list now of some things I may order just to replace for the sake of doing so: new breather cap, new filler cap (PO sort of rounded off the corners of that a little, so he likely used too much effort to tighten it at some point), and new filler cap o-ring. Teflon tape on the filler cap threads sounds like a great immediate test if I were actually able to ride now to test (currently 12F and snowing where I'm at). :(
 
Joined
Sep 4, 2013
Messages
8,114
Location
Cleveland
Bike
2010 ST1300
I hate to agree with Mr. Bush, but :plus1:

Remove the fill plug and try wrapping a few turns of teflon tape to threads of the plug before re-installing it. Check to make sure the cap isn't cracked. I understand that's easy to do, if it is tightened too much.

80W was recommended way back when the bike was manufactured, but that is ancient, now. I use 80W-90 ( regular or synthetic ) or 80-140 synthetic , BTW w/o any seepage.
Teflon tape is a great idea for most sealing plugs on the bike. I've read it is not suggested for the bleeder valves on the calipers because you don't want any teflon to be sucked into the caliper. Not sure if there is any suction in there, so its an individual choice, but careful application of the tape seems like a good idea.

You might read this Link about your gear oil choice - it's not what Honda recommends. Again its an individual choice.
 

paulcb

- - - Tetelestai - - - R.I.P. - 2022/05/26
Rest In Peace
Joined
Jun 4, 2013
Messages
4,652
Location
Celina, TX
Bike
'97/'01 ST1100 ABSII
STOC #
8735
Order an extra filler cap... they're aluminum, very easy to shear in half due to the hollow design. DAMHIK! ;)

When tightening, remember it's the o-ring under compression that creates the seal, not the contact of the two metal faces. Just snug the cap after the two metal faces meet.
 
Last edited:
Joined
Mar 13, 2012
Messages
5,047
Location
soCal
Bike
'97 ST1100
STOC #
687
The filler plug area appears to be the wettest, so my guess would be you need a new o-ring on that filler cap . . . or, it is loose.
That would be my first approach too, its cheap and easy, so nothing to lose. Also, that plug looks like someone removed it with ChannelLocks or something, its got several large pits in the hex surface where an improper tool was used. Make sure none of those pits are actually small holes.
 
Joined
Oct 25, 2013
Messages
9
Location
denmark
Bike
ST1100
The filler plug/cap on mine st had a very small crack (previous owner over tightened) and my st did the same thing. The lower housing of the final drive was greasy. Hope that your plug fix will be just as easy :)
 
Joined
Feb 29, 2016
Messages
195
Location
New York
If the vent was leaking wouldnt it be covered in oil too and the area immediately under it?

But its not.

Im thinking someone got a little too much moly on the splines the last tire change. Wipe the area with a finger and sniff. Is it gear oil or moly? :confused:
 
Joined
Jun 3, 2006
Messages
3,512
Location
British Columbia
Bike
2021 RE Meteor 350
If the vent was leaking wouldnt it be covered in oil too and the area immediately under it?

But its not.

Im thinking someone got a little too much moly on the splines the last tire change. Wipe the area with a finger and sniff. Is it gear oil or moly? :confused:
You are right, it isn't the vent. That is plainly visible.

However, it can't be Moly either. If it were, it would be on the other side of the wheel and besides, Moly does not "flow" under high temperature. Too much will just fling off all around the inner hub/spline area.
 
Joined
Feb 29, 2016
Messages
195
Location
New York
You are right, it isn't the vent. That is plainly visible.

However, it can't be Moly either. If it were, it would be on the other side of the wheel and besides, Moly does not "flow" under high temperature. Too much will just fling off all around the inner hub/spline area.

Probably. But I still am requesting a sniff test, just to remove all doubt.:)
 
Top Bottom